@article{SchultzFenskeDionBertrandetal., author = {Schultz, Christof and Fenske, Markus and Dion-Bertrand, Laura-Isabelle and G{\´e}linas, Guillaume and Marcet, St{\´e}phane and Dagar, Janardan and Bartelt, Andreas and Schlatmann, Rutger and Unger, Eva and Stegemann, Bert}, title = {Hyperspectral Photoluminescence Imaging for Spatially Resolved Determination of Electrical Parameters of Laser-Patterned Perovskite Solar Cells}, series = {Solar RRL}, volume = {7}, journal = {Solar RRL}, number = {22}, publisher = {Wiley}, issn = {2367-198X}, doi = {10.1002/solr.202300538}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-18215}, abstract = {Absolute calibrated hyperspectral photoluminescence (PL) imaging is utilized to access, in a simple and fast way, the spatial distribution of relevant solar cell parameters such as quasi-Fermi level splitting, optical diode factor, Urbach energies Eu, and shunt resistances Rsh, without the need for electrical measurements. Since these metrics play a significant role in evaluating the process windows for electrical series interconnection by laser patterning, this approach is followed to systematically locate and quantify electrical losses that may occur as a result of the laser-patterning process for monolithic series interconnection. It is shown that both picosecond and nanosecond laser pulses can be used for successful series interconnection. In both cases, only minor lateral material alterations occur, localized in a few μm wide region adjacent to the edges of the scribe lines. Furthermore, the acquisition and analysis of these hyperspectral PL datasets provide insights in the material removal process, from which it is concluded that the perovskite is rather resilient against the thermal impact of the laser.}, subject = {Laserablation}, language = {en} } @article{YetkinKodalleBertrametal., author = {Yetkin, Hasan A. and Kodalle, Tim and Bertram, Tobias and Villanueva-Tovar, Alejandra and Rusu, Marin and Klenk, Reiner and Szyszka, Bernd and Schlatmann, Rutger and Kaufmann, Christian A.}, title = {Decay mechanisms in CdS-buffered Cu(In,Ga)Se2 thin-film solar cells after exposure to thermal stress: Understanding the role of Na}, series = {Progress in Photovoltaics: Research and Applications}, volume = {29}, journal = {Progress in Photovoltaics: Research and Applications}, number = {9}, publisher = {Wiley}, doi = {10.1002/pip.3438}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-15138}, pages = {1034 -- 1053}, abstract = {Due to their tunable bandgap energy, Cu(In,Ga)Se2 (CIGSe) thin-film solar cells are an attractive option for use as bottom devices in tandem configurations. In monolithic tandem devices, the thermal stability of the bottom device is paramount for reliable application. Ideally, it will permit the processing of a top device at the required optimum process temperature. Here, we investigate the degradation behavior of chemical bath deposited (CBD) CdS-buffered CIGSe thin-film solar cells with and without Na incorporation under thermal stress in ambient air and vacuum with the aim to gain a more detailed understanding of their degradation mechanisms. For the devices studied, we observe severe degradation after annealing at 300°C independent of the atmosphere. The electrical and compositional properties of the samples before and after a defined application of thermal stress are studied. In good agreement with literature reports, we find pronounced Cd diffusion into the CIGS absorber layer. In addition, for Na-containing samples, the observed degradation can be mainly explained by the formation of Na-induced acceptor states in the TCO front contact and a back contact barrier formation due to the out-diffusion of Na. Supported by numerical device simulation using SCAPS-1D, various possible degradation models are discussed and correlated with our findings.}, language = {en} } @article{KoehnenWagnerLangetal., author = {K{\"o}hnen, Eike and Wagner, Philipp and Lang, Felix and Cruz, Alexandros and Li, Bor and Roß, Marcel and Jošt, Marko and Morales-Vilches, Anna B. and Topič, Marko and Stolterfoht, Martin and Neher, Dieter and Korte, Lars and Rech, Bernd and Schlatmann, Rutger and Stannowski, Bernd and Albrecht, Steve}, title = {27.9\% Efficient Monolithic Perovskite/Silicon Tandem Solar Cells on Industry Compatible Bottom Cells}, series = {Solar RRL}, volume = {5}, journal = {Solar RRL}, number = {7}, publisher = {Wiley}, doi = {10.1002/solr.202100244}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-15145}, pages = {8}, abstract = {Monolithic perovskite/silicon tandem solar cells recently surpass the efficiency of silicon single-junction solar cells. Most tandem cells utilize >250 μm thick, planarized float-zone (FZ) silicon, which is not compatible with commercial production using <200 μm thick Czochralski (CZ) silicon. The perovskite/silicon tandem cells based on industrially relevant 100 μm thick CZ-silicon without mechanical planarization are demonstrated. The best power conversion efficiency (PCE) of 27.9\% is only marginally below the 28.2\% reference value obtained on the commonly used front-side polished FZ-Si, which are about three times thicker. With both wafer types showing the same median PCE of 27.8\%, the thin CZ-Si-based devices are preferred for economic reasons. To investigate perspectives for improved current matching and, therefore, further efficiency improvement, optical simulations with planar and textured silicon have been conducted: the perovskite's bandgap needs to be increased by ≈0.02 eV when reducing the silicon thickness from 280 to 100 μm. The need for bandgap enlargement has a strong impact on future tandem developments ensuring photostable compositions with lossless interfaces at bandgaps around or above 1.7 eV.}, language = {en} } @article{VillanuevaTovarKodalleKaufmannetal., author = {Villanueva-Tovar, Alejandra and Kodalle, Tim and Kaufmann, Christian A. and Schlatmann, Rutger and Klenk, Reiner}, title = {Limitation of Current Transport across the Heterojunction in Cu(In,Ga)Se2 Solar Cells Prepared with Alkali Fluoride Postdeposition Treatment}, series = {Solar RRL}, volume = {4}, journal = {Solar RRL}, number = {4}, doi = {10.1002/solr.201900560}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-14503}, abstract = {Postdeposition treatments (PDTs) of chalcopyrite absorbers with alkali fluorides have contributed to improving the efficiency of corresponding solar cell devices. However, cells prepared with PDTs also tend to exhibit nonideal current-voltage (J-V) characteristics especially at low temperatures. These include blocking of the forward diode current, saturation of the open-circuit voltage with respect to temperature, a discrepancy between dark and Jsc (Voc) characteristics, and a crossover between dark and light J-V curves. These are typical observations while measuring the temperature-dependent J-V characteristics. Herein, the influence of electronic material parameters on the blocking of the current across the heterojunction in numerical simulations is reported. It is shown that a low-doped ZnO window layer, acceptor defects at the CdS/ZnO interface, or a high band offset at that interface lead to similar nonideal J-V characteristics, suggesting that the carrier density in the buffer layer is a crucial parameter for the current limitation. Connections between the effects of PDT previously reported in literature and the electronic material parameters considered in the numerical model are discussed to explain the nonideal J-V characteristics caused by the PDTs.}, language = {en} } @article{FenskeSchultzDagaretal., author = {Fenske, Markus and Schultz, Christof and Dagar, Janardan and Kosasih, Felix Utama and Zeiser, Andreas and Junghans, Cornelia and Bartelt, Andreas and Ducati, Caterina and Schlatmann, Rutger and Unger, Eva and Stegemann, Bert}, title = {Improved Electrical Performance of Perovskite Photovoltaic Mini-Modules through Controlled PbI2 Formation Using Nanosecond Laser Pulses for P3 Patterning}, series = {Energy Technology}, volume = {9}, journal = {Energy Technology}, number = {4}, doi = {10.1002/ente.202000969}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-15841}, pages = {1 -- 8}, abstract = {The upscaling of perovskite solar cells to modules requires the patterning of the layer stack in individual cells that are monolithically interconnected in series. This interconnection scheme is composed of three lines, P1-P3, which are scribed using a pulsed laser beam. The P3 scribe is intended to isolate the back contact layer of neighboring cells, but is often affected by undesired effects such as back contact delamination, flaking, and poor electrical isolation. Herein, the influence of the laser pulse duration on the electrical and compositional properties of P3 scribe lines is investigated. The results show that both nanosecond and picosecond laser pulses are suitable for P3 patterning, with the nanosecond pulses leading to a higher open circuit voltage, a higher fill factor, and a higher power conversion efficiency. It is found that the longer pulse duration resultes in a larger amount of PbI2 formed within the P3 line and a thin Br-rich interfacial layer which both effectively passivate defects at the scribe line edges and block charge carrier in its vicinity. Thus, nanosecond laser pulses are preferable for P3 patterning as they promote the formation of beneficial chemical phases, resulting in an improved photovoltaic performance.}, subject = {Laserablation}, language = {en} } @article{DagarParamasivamKlimmetal., author = {Dagar, Janardan and Paramasivam, Gopinath and Klimm, Carola and Fenske, Markus and Schultz, Christof and Schlatmann, Rutger and Stegemann, Bert and Unger, Eva}, title = {Stability Assessment of p-i-n Perovskite Photovoltaic Mini-Modules Utilizing Different Top Metal Electrodes}, series = {Micromachines}, volume = {12}, journal = {Micromachines}, number = {4}, publisher = {MDPI}, issn = {2072-666X}, doi = {10.3390/mi12040423}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-14784}, pages = {8}, abstract = {Long-term stability is one of the major challenges for p-i-n type perovskite solar modules (PSMs). Here, we demonstrate the fabrication of fully laser-patterned series interconnected p-i-n perovskite mini-modules, in which either single Cu or Ag layers are compared with Cu/Au metalbilayer top electrodes. According to the scanning electron microscopy measurements, we found that Cu or Ag top electrodes often exhibit flaking of the metal upon P3 (top contact removal) laser patterning. For Cu/Au bilayer top electrodes, metal flaking may cause intermittent short-circuits between interconnected sub-cells during operation, resulting in fluctuations in the maximum power point (MPP). Here, we demonstrate Cu/Au metal-bilayer-based PSMs with an efficiency of 18.9\% on an active area of 2.2 cm2 under continuous 1-sun illumination. This work highlights the importance of optimizing the top-contact composition to tackle the operational stability of mini-modules, and could help to improve the feasibility of large-area module deployment for the commercialization of perovskite photovoltaics.}, language = {en} } @article{XiaoErfurtFelixetal., author = {Xiao, Ting and Erfurt, Darja and F{\´e}lix, Roberto and Liao, Xiaxia and Frisch, Johannes and Abou-Ras, Daniel and Mazzio, Katherine A. and Wilks, Regan G. and Schlatmann, Rutger and B{\"a}r, Marcus}, title = {Annealing-Induced Chemical Interaction at the Ag/In2O3:H Interface as Revealed by In Situ Photoelectron Spectroscopy}, series = {Advanced Materials Interfaces}, volume = {10}, journal = {Advanced Materials Interfaces}, number = {11}, doi = {10.1002/admi.202202347}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-16896}, abstract = {Hydrogen-doped In2O3 (In2O3:H) is highly conductive while maintaining extraordinary transparency, thus making it a very attractive material for applications in optoelectronic devices such as (multijunction) solar cells or light-emitting devices. However, the corresponding metal/In2O3:H contacts may exhibit undesirably high resistances, significantly deteriorating device performance. To gain insight into the underlying efficiency-limiting mechanism, hard X-ray photoelectron spectroscopy is employed to in-situ monitor annealing-induced changes in the chemical structure of the Ag/In2O3:H interface system that is further complemented by ex-situ electron microscopy analyses and contact resistance measurements. The observed evolution of the Ag- and In-related photoelectron line intensities can be explained by significant intermixing across the Ag/In2O3:H interface. The corresponding lineshape broadening of the Ag 3d spectra is attributed to the formation of Ag2O and AgO, which becomes significant at temperatures above approximately 160 °C. However, after annealing to 300 °C, instead of the formation of an insulating AgOx interfacial layer, it is found i) In to be rather homogeneously distributed in the complete Ag/In2O3:H stack, ii) Ag diffusing into the In2O3:H, and iii) an improvement of the contact resistance rather than its often-reported deterioration.}, subject = {Wasserstoff}, language = {en} } @article{KemppainenBagackiScharyetal., author = {Kemppainen, Erno and Bagacki, Rory and Schary, Christian and Bao, Fuxi and Dorbandt, Iris and Janke, Stefan and Emery, Quiterie and Stannowski, Bernd and Schlatmann, Rutger and Calnan, Sonya}, title = {Dynamic Operation of a Heat Exchanger in a Thermally Integrated Photovoltaic Electrolyzer}, series = {Energy Technology}, volume = {11}, journal = {Energy Technology}, number = {2}, doi = {10.1002/ente.202201081}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-16903}, abstract = {The outdoor operation of an up-scaled thermally photovoltaic electrolyzer (PV EC), constructed using a heat exchanger (HE) made of low-cost materials, compared to its nonintegrated counterpart to quantify heat transfer and its effects, is studied. Thermal coupling of the PV and EC can reduce the difference between their temperatures, benefitting device performance. Such devices can produce hydrogen at rooftop installations of small-to-medium-sized nonindustrial buildings. The devices are tested outdoors using automated real-time monitoring. Under ≈880 W m-2 peak irradiance, they produced hydrogen at ≈120 and ≈110 mL min-1 rate with and without HE, respectively, corresponding to about 8.5\% and 7.8\% solar-to-hydrogen efficiencies. During about 700 h of testing, the HE is beneficial at over ≈500 W m-2 due to cyclic device operation. Under lower irradiance levels, pumping previously heated electrolyte through the HE increases the PV and reduces the electrolyte temperature, reducing the device performance. The HE increases the cumulative hydrogen production (≈800 L from both devices), so even relatively modest heat transfer rates can improve the PV EC operation. Improving the HE should further increase the benefits, but additional measures may be needed to maximize the hydrogen production.}, subject = {W{\"a}rmeaustauscher}, language = {en} } @article{CalnanAschbrennerBaoetal., author = {Calnan, Sonya and Aschbrenner, Stefan and Bao, Fuxi and Kemppainen, Erno and Dorbandt, Iris and Schlatmann, Rutger}, title = {Prospects for Hermetic Sealing of Scaled-Up Photoelectrochemical Hydrogen Generators for Reliable and Risk Free Operation}, series = {Energies}, volume = {12}, journal = {Energies}, number = {21}, publisher = {MDPI}, issn = {1996-1073}, doi = {10.3390/en12214176}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-3878}, pages = {29}, abstract = {Photo-electrochemical (PEC) systems have the potential to contribute to de-carbonation of the global energy supply because solar energy can be directly converted to hydrogen, which can be burnt without the release of greenhouse gases. However, meaningful deployment of PEC technology in the global energy system, even when highly efficient scaled up devices become available, shall only be a reality when their safe and reliable operation can be guaranteed over several years of service life. The first part of this review discusses the importance of hermetic sealing of up scaled PEC device provided by the casing and sealing joints from a reliability and risk perspective. The second part of the review presents a survey of fully functional devices and early stage demonstrators and uses this to establish the extent to which the state of the art in PEC device design address the issue of hermetic sealing. The survey revealed that current material choices and sealing techniques are still unsuitable for scale-up and commercialization. Accordingly, we examined possible synergies with related photovoltaic and electrochemical devices that have been commericalised, and derived therefrom, recommendations for future research routes that could accelerate the development of hermetic seals of PEC devices.}, language = {en} } @article{ErdilKhenkinRemecetal., author = {Erdil, Ulas and Khenkin, Mark and Remec, Marko and Emery, Quiterie and Sudhakar, Vediappan and Schlatmann, Rutger and Abate, Antonio and Katz, Eugene A. and Ulbrich, Carolin}, title = {Mimicking Outdoor Ion Migration in Perovskite Solar Cells: A Forward Bias, No-Light Accelerated Aging Approach}, series = {ACS Energy Letters}, volume = {10}, journal = {ACS Energy Letters}, number = {3}, publisher = {American Chemical Society}, issn = {2380-8195}, doi = {10.1021/acsenergylett.5c00376}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-20205}, pages = {1529 -- 1537}, abstract = {Perovskite solar cells (PSCs) are expected to transform the photovoltaic market; however, their unproven operational stability requires urgent attention, particularly accelerated aging tests. Currently, illumination is the primary stressor in such tests. In this work, we present an accelerated aging procedure consisting of prolonged forward biasing followed by a dark storage (postbias rest) phase, conducted entirely in the dark. During aging under forward bias, ion migration led to impeded charge transport, macroscopic defect growth, and an adverse response of the cells to short light soaking, all of which recovered in the postbias rest phase, yet resulted in increased recombination due to redistribution of ions. We found that outdoor operation of PSCs in Berlin, Germany, over a 20-month period exhibited similar dynamics, with periods of higher temperature and irradiance (spring-summer) aligning with the forward bias phase and cooler, dimmer periods (fall-winter) aligning with the postbias rest phase. This paves the way for accelerated aging tests that can mimic ion migration-induced degradation outdoors without requiring an illumination source.}, subject = {Perowskit}, language = {en} } @article{ErdilKhenkinBernardesdeAraujoetal., author = {Erdil, Ulas and Khenkin, Mark and Bernardes de Araujo, Wander Max and Emery, Quiterie and Lauermann, Iver and Paraskeva, Vasiliki and Norton, Matthew and Vediappan, Sudhakar and Kumar, D. Kishore and Gupta, Ritesh Kant and Visoly-Fisher, Iris and Hadjipanayi, Maria and Georghiou, George E. and Schlatmann, Rutger and Abate, Antonio and Katz, Eugene A. and Ulbrich, Carolin}, title = {Delamination of Perovskite Solar Cells in Thermal Cycling and Outdoor Tests}, series = {Energy Technology}, volume = {13}, journal = {Energy Technology}, number = {1}, issn = {2194-4288}, doi = {10.1002/ente.202401280}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-19632}, pages = {7}, abstract = {For the commercialization of perovskite solar cells (PSCs), detection of associated degradation mechanisms and mitigation of their effect is of paramount importance. The former requires outdoor and indoor stability tests to detect these mechanisms under real operation conditions and to accelerate them under controlled environments. Herein, the thermomechanical stability of encapsulated PSCs in outdoor tests at three locations coupled with indoor thermal cycling tests is investigated. Results show that encapsulant-induced partial delamination can occur in outdoor and indoor tests, leading to disruption in device integrity and substantial loss in the cell active area and short-circuit current. The findings suggest that delamination involves C60 and SnO2 layers as the mechanically weakest point in the device stack. To the best of our knowledge, this work is the first demonstration of delamination in encapsulated PSCs under real operation conditions. While partial delamination emerged on some of the cells exposed in Israel and Cyprus in just a few weeks, it did not occur in Germany over 2.5 years of outdoor exposure. This highlights the importance of multiclimate outdoor testing to validate the significance of failure modes observed through accelerated indoor testing.}, subject = {Delamination}, language = {en} } @article{SchultzFenskeOttoetal., author = {Schultz, Christof and Fenske, Markus and Otto, Nicolas and Dion-Bertrand, Laura-Isabelle and G{\´e}linas, Guillaume and Marcet, St{\´e}phane and Dagar, Janardan and Schlatmann, Rutger and Unger, Eva and Stegemann, Bert}, title = {Loss Analysis of P3 Laser Patterning of Perovskite Solar Cells via Hyperspectral Photoluminescence Imaging}, series = {Solar}, volume = {5}, journal = {Solar}, number = {2}, editor = {Boucl{\´e}, Johann}, publisher = {MDPI}, issn = {2673-9941}, doi = {10.3390/solar5020013}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-20545}, abstract = {Upscaling perovskite solar cells and modules requires precise laser patterning for series interconnection and spatial characterization of cell parameters to understand laser-material interactions and their impact on performance. This study investigates the use of nanosecond (ns) and picosecond (ps) laser pulses at varying fluences for the P3 patterning step of perovskite solar cells. Hyperspectral photoluminescence (PL) imaging was employed to map key parameters such as optical bandgap energy, Urbach energy, and shunt resistance. The mappings were correlated with electrical measurements, revealing that both ns and ps lasers can be utilized for effective series interconnections with minimal performance losses at optimized fluences. Our findings provide a deeper understanding of fluence-dependent effects in P3 patterning. Moreover, the results demonstrate that the process window is robust, allowing for reasonable cell performance even with deviations from optimal parameters. This robustness, coupled with the scalability of the laser patterning process, emphasize its suitability for industrial module production.}, subject = {Photoluminescence}, language = {en} } @article{BagackiReinhardtSchlatmannetal., author = {Bagacki, Rory and Reinhardt, Maximilian and Schlatmann, Rutger and Calnan, Sonya and van de Krol, Roel and Browne, Michelle P.}, title = {Electrochemical hydrogen pumps: a researcher's guide and review}, series = {Chemical Communications}, volume = {61}, journal = {Chemical Communications}, number = {56}, publisher = {The Royal Society of Chemistry}, issn = {1359-7345}, doi = {10.1039/d5cc01815c}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-21017}, pages = {10210 -- 10227}, abstract = {Hydrogen is considered an attractive energy vector and an indispensable base chemical for a wide variety of chemical products. As more hydrogen is produced via electrolysis, finding ways to store the H2 will become increasingly important due to the low volumetric energy density at ambient pressure. While high pressure storage is favoured for many applications, compressing hydrogen poses distinct challenges due to its low density and high diffusivity. Electrochemical hydrogen pumps (EHP) present a solution to this challenge by efficiently compressing hydrogen. Hydrogen compression is more efficient using electrochemical hydrogen pumps than conventional mechanical compressors because they operate through isothermal rather than adiabatic compression. Additionally, they can be used to separate hydrogen from gas mixtures, for example from natural gas pipelines supplemented with hydrogen, creating the possibility of integrating them with existing energy transport infrastructure. This paper summarizes recent progress in electrochemical hydrogen pump research and presents a case study on an EHP test cell, test rig and a measurement guide to advance research in this field. Although electrochemical hydrogen pumps offer many advantages, shortcomings remain, including the lack of standardized measurement conditions and procedures, as well as a limited understanding of degradation mechanisms. This review aims to provide insights into these issues and discuss future directions for electrochemical hydrogen pump research.}, language = {en} } @article{FariasBasultoMehlhopOttoetal., author = {Farias-Basulto, Guillermo and Mehlhop, Thede and Otto, Nicolas J. and Bertram, Tobias and Jäger, Klaus and Gall, Stefan and Weinberger, Nikolaus and Schlatmann, Rutger and Lauermann, Iver and Klenk, Reiner and List-Kratochvil, Emil and Kaufmann, Christian A.}, title = {Improving Perovskite/CIGS Tandem Solar Cells for Higher Power Conversion Efficiency through Light Management and Bandgap Engineering}, series = {ACS Applied Materials \& Interfaces}, volume = {17}, journal = {ACS Applied Materials \& Interfaces}, number = {40}, publisher = {American Chemical Society}, issn = {1944-8244}, doi = {10.1021/acsami.5c15458}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-21725}, pages = {56250 -- 56255}, abstract = {Perovskite and chalcopyrite materials are excellent absorbers for highly efficient, all-thin-film tandem solar cells. This work presents a certified world record for such a device, achieving a power conversion efficiency of 24.6 ± 1.1\% under steady-state conditions. The best IV parameters extracted from certified current-voltage measurements presented a short-circuit current density of around 19.3 mA/cm 2 , an open-circuit voltage of 1.765 V, and a fill factor of 71.8\%. In comparison to our previous record, the current density improved considerably, mainly due to the lowering of the bandgap of the bottom subcell and the improved optics of the top perovskite cell.}, subject = {Photovoltaic}, language = {en} } @article{Farias‐BasultoKafedjiskaBertrametal., author = {Farias-Basulto, Guillermo and Kafedjiska, Ivona and Bertram, Tobias and Riedel, Maximilian and Emery, Quiterie and Remec, Marko and Graniero, Paolo and Khenkin, Mark and Kaufmann, Christian A. and Lauermann, Iver and Klenk, Reiner and Schlatmann, Rutger and Ulbrich, Carolin}, title = {Perovskite-CIGSe Tandem Solar Cell: Over One Year of Outdoor Monitoring}, series = {Advanced Energy and Sustainability Research}, volume = {6}, journal = {Advanced Energy and Sustainability Research}, number = {12}, issn = {2699-9412}, doi = {10.1002/aesr.202500162}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-22159}, pages = {11}, abstract = {Tandem solar cells can surpass the limitations of single-junction devices, promising increased performance due to lower thermalization losses. Even though many research and industrial upscaling efforts are based on perovskite-Si tandems, all-thin-film photovoltaic (PV) devices, for instance with chalcopyrite (CIGSe) and perovskite, can offer many advantages such as significant cost and material savings and access to niche markets like building integrated- and flexible PV. However, long-term stability and outdoor performance of perovskite-based tandem devices is to this day challenging. This work presents the first data analysis of year-round outdoor measurements (mpp-tracked) of a perovskite-chalcopyrite tandem device with a starting efficiency of about 23.14\% before encapsulation. The maximum outdoor performance of the tandem device changed during the period of observation, reaching the peak performance in April and then decreased due to the device degradation. At its maximum outdoor performance, the tandem could reach up to 68\% higher instantaneous power output, relative to its single-junction reference (CIGSe-SJ). In addition, a quantitative time series performance analysis, exemplary qualitative imaging characterization of the tandem before and after outdoor exposure, is shown. Finally, the possibility of predicting the immediate performance of an all-thin-film tandem is verified by using a multiple linear regression model with accuracies generally exceeding 90\%.}, subject = {Machine learning}, language = {en} } @article{KafedjiskaLeCorreKoebleretal., author = {Kafedjiska, Ivona and Le Corre, Vincent M. and K{\"o}bler, Hans and Levine, Igal and Schlatmann, Rutger and Lauermann, Iver}, title = {Investigation of interfacial charge-carrier dynamics, degradation, and recombination mechanisms in single-junction perovskite solar cells with NiOx and SAM hole-transporting layers via steady-state drift-diffusion model simulations}, series = {Sustainable Energy \& Fuels}, volume = {10}, journal = {Sustainable Energy \& Fuels}, number = {4}, publisher = {The Royal Society of Chemistry}, issn = {2398-4902}, doi = {10.1039/d5se00474h}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:523-22345}, pages = {1174 -- 1191}, abstract = {We investigate the stability and the degradation pathways in single-junction perovskite solar cells with four varying hole-transporting layers (HTLs): pure nickel oxide (NiOx) and copper-doped (NiOx:Cu), with or without self-assembled monolayer (SAM) surface passivation. The cells are aged in a continuous MPP-tracking set-up in a nitrogen environment at 25 °C and the JV curves prior to and after the aging are fitted via drift-diffusion simulations. By using a set of experimentally-measured input parameters and correlating the results from the experiments with the simulations, we are able to test the reliability of the model and then extract important information about the interfacial charge-carrier dynamics, recombination, and degradation mechanisms in the solar cells. We find that NiOx induces severe electron trapping and poor band alignment at the NiOx-perovskite interface, thereby leading to the highest quasi-Fermi level splitting to open-circuit voltage (QFLS-Voc) offset among all the HTLs. As the cells age, the density of bulk traps when NiOx, NiOx:Cu, and NiOx:Cu + SAM are used increases by factors of 36, 3, and 8, respectively, while for NiOx + SAM it remains unchanged. For all of the HTLs, the non-radiative Shockley-Read-Hall (SRH) recombination via surface traps is the dominant recombination mechanism, as it is around 2-3 orders of magnitude higher than the direct or bulk-SRH recombination pathway. Additionally, NiOx exhibits an around 2 orders of magnitude higher rate of SRH interfacial recombination compared to the other three HTLs. However, as the cells age, the rate of the interface SRH recombination remains relatively stable, but the bulk SRH recombination increases by an order of magnitude in all cells, indicating that the degradation of the cells is directly proportional to the increase of the trap-assisted recombination in the perovskite bulk and its degradation. Finally, we investigate the correlation between the hysteresis factor (HF) and the ion concentration. We find that the devices with NiOx have the highest HF and the highest negative-ion concentration, in good agreement with the finding of electron trapping and the highest trap-assisted recombination rate for the NiOx samples. Combining all of this information, we can explain why NiOx is the least stable HTL among all the HTLs (15\% loss in the initial PCE) and how its stability can be improved with Cu doping (8\% loss in the initial PCE) and, to an extent, with SAM passivation (around 11\% loss in the initial PCE).}, language = {en} }